Most of the new cases were in the southern Guekedou region
Some 208 people have now died from the Ebola virus in Guinea after a deadly spike in recent days, world health officials say.
At least 21 people died and 37 new cases of suspected Ebola were found between 29 May and 1 June, bringing the total number of cases in the West African country to 328.
Of these, 193 have been confirmed by laboratory tests.
There is no cure or vaccine for Ebola – one of the world’s deadliest viruses.
More than half of the new deaths were in the southern Guekedou region, where the outbreak is centred.
Three confirmed and 10 suspected new cases were recorded in neighbouring Sierra Leone over the same period.
Six people are believed to have died there, as well as 10 in Liberia.
Medical charities say one reason for the increase is that some people are refusing to go to hospital for treatment, preferring to seek help from traditional healers.
Ebola, a haemorrhagic fever, can kill up to 90% of those infected and is passed on through contact with the fluids of infected people or animals, such as urine, sweat and blood.
But people have a better chance of surviving if it is identified early and they receive medical attention.
Experts from the World Health Organisation and the Doctors Without Borders charity are in the region, and about 600 people are under observation after having possible contact with Ebola.